Page:Science vol. 5.djvu/565

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��I -fieBseB employed, the book is well supplied with authentic illustrations, although ^ome of them are not verj- clear, — a fault doubtless due to imperfections in the original photographs.

��■ SOME STATE GEOLOGICAL REPORTS. Minnesota is not only the centre, but it is also the summit of the continent, in the sense of being the starling- point of the three most important systems of drainage in North Amer- ica. Sut, not with stand in); its ge<^raphic iK>si- tion, the mean altitude of the state is less than thirteen hundred feet, and its surface configu- ration presents the simplicity and monotony of a level and thoroughly glaciated region ; while

I the geological structure of the greater portion of the state is hopelessly buried under a thick and almost unbroken mantle of drift. These circumstances greatly diminish the labors of the geologist ; and it is at lirst a matter of •nrprise that ten years should have elapsed between the inception of the survey and the completion of this firat volume of the final report. But this is readily explained by the very economical administration of the survey, jttic geological corps consisting of the director and one assistant, and, during a considerable part of the time represented by this volume, of the director alone. The introductory chapter is an extended luid admirable historical sketch of explorations and surveys in Minnesota and the adjacent States, from the times of Cbamplain, Duluth, Hennepin, and La .Salle, to the present survey. This historical introduction is, in its extent and general interest, unique among American geological reports. It is illustrated by several good reductions of the earlier maps of the north-west, and must prove a valuable com- pilation to students of history and geography as well as of geology. The account of the general physical features of the state in this volume is brief, and vet adequate, considering the toimgraphic uniformity. But we look in vain for any generalized statement of the geo- logical formations of the state below the drift. It is probable, however, that this chapter is reserved for a later volunie ; for, as stated in the preface, this volume is intended to be mainly descriptive. — a repository of facts, with only such generalizations as are self- evident or generally admitted.

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��The popular demand for early practical re- sults is well met in the excellent chapter on the building-stones, which constitute, at pres- ent, the most important field of the economic geologist. The descriptions are plain and simple, with the condensed statements of the microscopic characters in fine print. The use of ' syenite ' aa a name for hornhlendic granite is, however, antiquated, and without the sanc- tion of the leading lithologists of this country and Europe. Tlie table in which the descrip- tions of forty-one of the most important build- ing-stones are condensed and compared would be a model of its kind, if the mineralogical composition of the stones were included. It shows at a glance, that, in crushing- strength and durability, the building- stones of Minne- sota are probably not surpassed by those of any state in the Union.

The main part of this volume (about five hundred pages) is devoted to detailed accounts of the geology of the state by counties. Of the eighty counties in the state, twenty-eight, including nearly all that part of the stale south of the Minnesota River, are here mapped and described, two-thirds of this work being cred- ited to Mr. Upham. In some instances the descriptions of several counties have been combined; and, if this plan bad been more generally adopted, much needless repelitioQ might have been avoided, and the monotony of this |Mirt of the volume greatly relieved.

The two annual reports of the state geologist of Indiana contain comparatively little in the way of original contributions to the geolc^y or natural history of the state. The most important sections of the reports are those on the paleozoic corals, and the sub carboniferous fossils of Spergen Hill, by Professor James Hal! ; the paleozoic flora, by Professor Lea- quereux ; and the fauna of the Indiana coal- measures, by Dr. C. A. White. These papers consist of short specific descriptions, with seventy-one plates of figures. Very few of the species are new to science, or peculiar to Indiana, while a considerable number are not found in that state. These articles are really compilations from the reports of other states and more general sources ; and, although doubt- less of some value as reference-manuals of the paleozoic fauna and flora, it is a question to what extent such publications are reallj- ger- mane to the purposes of a geological survc}'. Each volume contains several short county reports, and in these and other chapters the economic features have special prominence. But the treatment is not always impartial, for there is a manifest tendency in aQOie. "^asSa-^a

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